1. Technical Field
The present invention relates to a method of manufacturing a semiconductor device capable of improving close adherence of insulating interlayer.
2. Related Art
With the advances in dimensional shrinkage of silicon semiconductor integrated circuit (LSI), it has faced new difficulties in increase in power consumption and signal delay due to increased parasitic capacitance. Decrease in the dielectric constant of the insulating film is therefore indispensable to avoid these problems, and the situation has promoted adoption of porous insulating film. The porous insulating film is generally formed by a method of introducing porogen in the process of film growth, and then removing it typically by post-curing. The method has succeeded in obtaining an insulating interlayer having a dielectric constant of approximately 2.0 to 2.5.
Reduction of the dielectric constant as a result of introduction of pores is, however, causative of degradation in physical characteristics of the film, so that various improvements have been made to avoid the degradation.
For example, for the purpose of improving the inter-film close adherence of a SiCN film/low-k film (SiOC film) stacked structure, Japanese Laid-Open Patent Publication No. 2005-223012 discloses a method of varying flow rate of source material for forming the SiOC film, so as to make the density thereof elevated in a portion closer to the SiCN film, and decreased in a direction departing from SiCN film.
For the purpose of suppressing moisture adsorption of the insulating interlayer, Japanese Laid-Open Patent Publication No. 2007-142066 discloses a method of controlling the rate of growth of the film, making use of a high-frequency power of 13.56 MHz and a low-frequency power of 300 kHz or larger and 500 kHz or smaller.
For the purpose of ensuring a necessary level of reliability, Japanese Laid-Open Patent Publication No. 2005-223012 discloses a method of forming the film making use of high-frequency power and low-frequency power, and terminating the formation while step-wisely turning off these two levels of RF. According to the publication, the number of micro foreign matters on the surface of film may be reduced by turning off a high-frequency power source substantially earlier than a low-frequency power source.
International Patent Publications WO2008/10591 and WO2007/132879 disclose techniques of reducing dielectric constant of an insulating interlayer by introducing micro-pores in the film, in plasma polymerization using a cyclic monomer, or using a cyclic monomer and straight-chain monomer.
International Patent Publication WO2008/078649 discloses a method of forming a capping film using a barrier insulating film containing an unsaturated hydrocarbon and amorphous carbon, or using a double-layered structure composed of such barrier insulating film and an inner barrier insulating film composed of SiN, SiC, SiCN or the like, to thereby improve the barrier function against diffusion.
Japanese Laid-Open Patent Publication No. 2003-234346 describes a method of forming a barrier insulating film, by supplying high-frequency power to one electrode of a plasma chamber, and by supplying a low-frequency power of 50 kHz or larger and smaller than 1 MHz to the opposite electrode only in an early stage of formation of the film.